1. Field of the Invention
The present invention relates to a recording/reproducing apparatus for optically recording and reproducing information on an optical tape having a thermal converting layer, and more particularly, to a recording/reproducing apparatus for an optical tape which optically performs recording, reproducing and erasing of information.
2. Description of the Related Art
U.S. Pat. No. 4,398,203 discloses an optical tape having a thermal converting layer. Bumps are formed on the thermal converting layer when it is heated. The bumps remain even after cooling. Also, when the thermal converting layer is re-heated by a predetermined thermal energy, the bumps disappear and the thermal converting layer is restored to its original smooth state. Therefore, it is possible to optically record/reproduce information using an optical recording medium having such a thermal converting layer. That is, the information is optically recorded by scanning a focussed light on the optical recording medium and modulating the light according to the desired information. Then, the information is optically reproduced by directing scanning light, having an energy which is too low to affect the thermal converting layer, toward the optical recording medium and detecting the light reflected therefrom.
Such an optical recording medium having a thermal converting layer can be produced in the form of a tape, similar to a magnetic recording tape, so that it can store more information than a conventional disk-type optical recording medium.
FIG. 1 shows a conventional optical recording/reproducing apparatus using such an optical recording medium formed as a tape having a thermal converting layer. The apparatus uses an optical tape 1 wound on a pair of reels 2 and 3 and received in a cassette 4. Optical tape 1 starts from one reel 2, sequentially passes near a heating head 5 for erasing and an optical pickup 6, for recording/reproducing, and is wound to the other reel 3. During recording, heating head 5 is heated to raise the temperature of, and slightly press, optical tape 1, and, at the same time, a light for recording having a predetermined energy is radiated from optical pickup 6 for recording data. When heating head 5 is withdrawn, a light for reproducing, having another predetermined energy which is lower than that of the recording light, is radiated from optical pickup 6 so as to record data. A cooler (not shown) may be added for cooling the tape down to a proper temperature for recording after optical tape 1 is heated by heating head 5 and before it reaches optical pickup 6.
Optical pickup 6, in the conventional apparatus, is shown in FIG. 2. Two laser diodes 61 and 61' are provided to radiate light beams having different amounts of energy for recording and reproducing, respectively. Beam splitters 62 and 62', deflection beam splitters 63 and 63', and phase plates 64 and 64' are also provided. Also, a galvanometer mirror 66 is installed in front of an objective lens 65. A detecting optical system 67 is constituted by a plurality of detecting lens and photodiodes for tracking/focusing servo operation during reproducing.
In such a conventional device, time is required for heating head 5 to be heated to a predetermined temperature during recording. Also, since a separate cooler is required its design is difficult and the cost is increased. Also, galvanometer mirror 66 must be operated during a reproducing operation resulting in excessive power consumption and mechanical noise generation.